Phosphodiesterases (PDE) control intracellular cyclic adenosine monophosphate (cAMP) levels, which appear to play an important role in the regulation of inflammation. PDE4B is especially important in this process. Using in situ hybridization histochemistry we first mapped the expression sites of the four PDE4B splicing forms in rat brain. Using the systemic administration of the bacterial endotoxin lipopolysaccharide (LPS) as an inflammation model in rats, we found an increase in PDEB2 mRNA expression in choroid plexus. The differential expression of PDE4B spliced forms and the differential regulation of PDE4B2 in an inflammatory model further supports an involvement of this splicing variant in the inflammatory response.